Conventionally, during formation of a permanent pattern of solder resist or the like, a photosensitive layer is formed on an intended member by using a method in which a liquid of photosensitive composition is applied by spin coating, screen printing, or spray printing to form a coated film and then dried, or a method in which a photosensitive composition is applied and dried on a temporary support to form a laminate film having a photosensitive layer and then only the photosensitive layer is transferred on the member by a vacuum laminator or a roll laminator. As a method for forming a permanent pattern of solder resist or the like, for example, there is known a method in which a photosensitive layer is formed on a silicon wafer on which the permanent pattern is to be formed, on a wired silicon wafer, or on a substrate such as a copper-coated laminate plate by using a method as above; the photosensitive layer of the laminate is subjected to exposure; after the exposure, the photosensitive layer is developed to form a pattern; and then, curing treatment and the like are performed to form the permanent pattern.
The formation of the permanent pattern is also applied to a package substrate interposed between a semiconductor chip and a printed board. Regarding the package substrate, much higher density packaging has been demanded in recent years. Wiring pitch width is being narrowed, solder resist layer strength is increasing, and insulating properties of the layer are improving, whereas thickness thereof is being reduced. Thus, there is a strong desire for more resistance to repeated hot and cold shocks (thermal cycling test resistance: TCT resistance). In addition, via diameter reduction and smoothness of tapered configuration are also desired in terms of mountability.
It is necessary for such a photosensitive composition used to form a solder resist to have excellent preservation stability from the viewpoint of convenience.
Meanwhile, a solid state imaging device (image sensor) used in mobile phones, digital cameras, digital video cameras, surveillance cameras, and the like is a photoelectric conversion device formed as an integrated circuit using a semiconductor device producing technique. Recently, due to size and weight reduction in mobile phones and digital cameras, further miniaturization of solid state image sensors has been desired.
To miniaturize the solid state image sensor, there has been proposed a technique for applying a through-electrode and forming a thinner silicon wafer (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2009-194396). Although miniaturization can be made by polishing and thinning of a silicon wafer, the thinned silicon wafer has come to easily transmit light having a wavelength of 800 nm or more, while maintaining shieldability of light of 800 nm or less. Therefore, a new problem has been found in which since photodiodes used in solid state image sensors respond even to light ranging from 800 to 1200 nm, transmission of light of 800 nm or more deteriorates image quality.
The solid state image sensor is configured to include photodiodes, a color filter and a lens, which are adjacent to one side of the photodiodes. Near the color filter or the lens is provided an infrared cut-off filter that cuts off infrared light ranging from 800 to 1200 nm. On an opposite side of the color filter are provided metal wires, a solder resist, and the like. The solder resist is often filled in between the metal wires. However, there has been a problem that it is impossible to shield infrared ray such as leaking light entering the inside of mobile phones, digital cameras, or the like. Thus, conventional measures have been taken to ensure infrared ray shielding properties by additionally disposing an infrared ray shielding layer outside the solder resist having insufficient infrared ray shielding properties. Nevertheless, in general, due to unevenness caused by wires and the like on the solder resist, it has been difficult to apply an even thickness of a material of the infrared ray shielding layer on the uneven surface of a substrate, so that there has been a problem in which a portion with insufficient thickness of the material transmits light therethrough.
To provide an infrared ray shielding layer only on a desired portion, it is preferable for the composition to exhibit photosensitivity and photolithography performance allowing for patterning by exposure. As a light-shielding photosensitive composition having the photolithography, there may be mentioned a black resist including carbon black used to form an LCD color filter. The carbon black has high visible-light shieldability, but has low infrared-ray shieldability. When using such a black resist as a solder resist, addition of carbon black in an amount ensuring shieldability required in infrared region excessively increases the shieldability in the visible light region. The resist will shield light having a shorter wavelength than visible light, which is used for exposure by a high pressure mercury vapor lamp, KrF, ArF, or the like, as usually used for image formation. Accordingly, there is a problem of insufficient photocurability.
Furthermore, at present, an infrared ray shielding layer is disposed separately after forming a solder resist by an applying method. Thus, due to the formation of the solder resist and the formation of the infrared ray shielding layer, it is necessary to perform steps for application, exposure, development, post-heating, and the like plural times. This results in complication of steps and increase of cost, so that improvement has been desired.
Then, an attempt to allow a solder resist itself to have shieldability has been made. For example, there has been proposed a black solder resist composition including a black colorant, a colorant other than black, and a polyfunctional epoxy compound (for example, see JP-A-2008-257045). The composition, however, is characterized in that the content of the black colorant is reduced by combination with the colorant other than black. Therefore, in terms of ensuring both light shielding properties particularly in infrared region and curability, the composition has been practically insufficient.